Yoshizawa–Randlett system

The Yoshizawa–Randlett system is a way to show how origami models are folded. It helps people understand the steps needed to make different origami designs. Many origami books start by teaching basic folding techniques, which are important for building the models.

There are also some common starting shapes, called bases, that are often used as the first step in making origami. Origami models are grouped based on how hard they are to make, with some needing only simple skills and others requiring more advanced techniques. This system makes it easier for everyone to follow along and enjoy creating origami.

History

The idea of making origami diagrams started with a book called “Senbazuru Orikata” in 1797. But the diagrams were not very clear and mostly just showed the final shape, leaving people unsure how to fold it.

Later, books tried different ways to show the folding steps, but none worked well for all models. In the 1950s and 1960s, Akira Yoshizawa created a new system of diagrams. He used dotted and dashed lines to show different folds and added a few special symbols. This idea was noticed by Samuel Randlett and Robert Harbin, who added more symbols. Their combined system, called the Yoshizawa–Randlett system, was first explained in Samuel Randlett's book Art of Origami in 1961. It became the standard way to make origami diagrams and is still used today.

Origami symbols

Origami symbols use lines and arrows to show how to fold paper. Arrows tell you how to bend or move the paper, while lines show different types of edges.

A thick line marks the edge of the paper. A dashed line shows a valley fold, where the paper folds in front of itself. A dashed and dotted line shows a mountain fold, where the paper folds behind itself. A thin line marks where a fold has already been creased. A dotted line shows a fold that is hidden or not yet made. Common folds include pleat folds and reverse folds, which are often done at an angle. Reverse folds of a corner can create shapes like feet or bird heads. The sink fold is a more advanced technique, with an open sink being easier and a closed sink creating a hidden pocket.

Compound folds

Origami has special ways to make folds called squash, rabbit ear, and petal folds. A squash fold begins with a flap that has at least two layers, like one part of a waterbomb base. You fold down from the point in the middle, open the flap, and then fold it again to make two new flaps next to each other.

A rabbit ear fold starts by making a crease across a diagonal. Then you fold from the corners along the same side of that crease, and fold the flap down so the edges line up.

A petal fold uses two connected flaps, each with at least two layers, like parts of a preliminary base. You attach these flaps along a crease, make folds from the open point, unfold, and then make a triangle of creases on top. After unfolding again, you fold one layer of the point up and flatten it using the creases you made. This fold is like having two rabbit ear folds side by side, connected along the crease.

Origami bases

In origami, many models start with a special folded shape called a base. These bases are the first steps before making the final shape. Some common bases include:

• The blintz base, made by folding the corners of a square into the center, like a small pancake. This creates a square that can be used to start folding many different models.
• The kite base, made by folding two edges of the square together along the diagonal.
• The fish base, which uses folds on opposite corners to create flaps that are folded downward.
• The waterbomb base, made by folding the square along its diagonals and then compressing it to form a triangle shape with flaps.
• The preliminary fold, also called the Square Base, which folds the corners and edges to make a square with triangular flaps.
• The bird base, or crane base, which starts with a preliminary fold and then folds the sides upward.
• The frog base, which begins with a waterbomb or preliminary fold and then folds the flaps and corners in special ways.

More advanced skills

Origami has many tricky folds that help create beautiful models. One of these is the swivel fold, where a piece of paper moves around a point. Another skill is the stretched bird base, where you adjust the shape of a basic bird form to make it flat.

There are also special folds like the open sink, where you reverse creases to form a shape in the middle of the model. The spread squash flattens a folded part, and the twist fold changes the angle of a section of paper. These advanced techniques are used in many complicated origami designs.